I use a desk bike. I work at home, so no boss to tell me I can't, fortunately. It's a great way to burn calories and keep up some activity even when you have to stay in the same place. With mine I need pretty good clearance under the desk, though, or to be able to move it out from under the desk. I have been happy with it.
Good luck. Sounds like you put in some long days. Your boss should understand you will feel better if you can move around some.